GSTM1 and gallstones: Significant differences in age (76 years vs. 69 years, respectively; P < 0.001), sex (74.0% vs. 62.2%, respectively; P = 0.021), presence of gallstones (76.4% vs. 86.4%, respectively; P = 0.015), severity grade I/III (28.5/35.8% vs. 47.6/13.0%, respectively; P < 0.001), ASA score ≥ 3 (58.5% vs. 34.1%, respectively; P < 0.001), Hb (12.8 mg/dl vs. 13.7 mg/dl, respectively; P < 0.001), Cr (0.9 mg/dl vs. 0.8 mg/dl, respectively; P < 0.001) and PT-INR (1.2 vs. 1.1, respectively; P < 0.001) were identified between the two groups.